1. Field of the Invention
The present invention relates to a magneto-optical head device and a recording and reproducing device employing the magneto-optical head device, which are applied to an external memory of an electronic computer or the like or used for recording and reproducing a video signal.
2. Description of the Background Art
An optical recording and reproducing method as well as a magnetic recording and reproducing method have recently been developed according to which information can be recorded at a high density to be reproduced. In the optical recording and reproducing method, the track density and line density of an optical disk are generally determined by the spot size of a light beam. On the other hand, in the magnetic recording and reproducing method, the line density of a magnetic disk is determined by a gap of a magnetic head and the track density is determined by the size of the magnetic head (in the direction of tracks). Therefore, generally the optical recording and reproducing method is superior in the track density and the magnetic recording and reproducing method is superior in the line density.
Japanese Patent No. 2617025 (hereinafter referred to as Reference 1) discloses a recording and reproducing method having both advantages of the optical recording and reproducing method and the magnetic recording and reproducing method, in other words, a recording and reproducing method which can implement both of the track density of the optical disk and the line density of the magnetic disk (hereinafter referred to as thermomagnetic recording and reproducing method). Reference 1 employs a ferromagnet as a medium (hereinafter referred to as thermomagnetic recording medium) which has a compensation temperature set at room temperature and generates a great magnetic flux when the temperature rises. Information is recorded by using an optical head to increase the temperature of the thermomagnetic recording medium and using the magnetic head to apply magnetic field to a portion where coercive force is reduced due to the increase in temperature. Information is reproduced by using the optical head to raise the temperature of the thermomagnetic recording medium and using the magnetic head to sense the magnetic flux generated from the portion where the temperature is increased.
According to this method, even if a magnetic head which is wide in he direction of tracks is used, high track density recording and reproduction is possible without causing cross light and crosstalk. Further, information in a region which is smaller than the spot size of light beam can be reproduced. Accordingly, both of the track density of the optical disk and the line density of the magnetic disk are implemented.
In the optical recording and reproducing method, a lens which is substantially hemispherical and called solid immersion lens (SIL) is used trying to reduce the spot size of light beam so as to enhance recording density. According to this method, the SIL is placed in an optical path of a light beam condensed by an objective lens, and the effective numerical aperture is converted by the SIL.
FIG. 1 illustrates a magneto-optical recording and reproducing method disclosed in Japanese Patent Laying-Open No. 10-162444 (hereinafter referred to as Reference 2) as one example of the optical recording and reproducing method using the SIL above. Details are given below in conjunction with this drawing.
A light beam is emitted from a light source (not shown) to be incident on an SIL 102 through an objective lens 106. In SIL 102, the wave length of the light beam is 1/n (n is refractive index) and the beam diameter is 1/n.
SIL 102 is adjacent to a magneto-optical recording medium 103 and the light beam which is incident on the magneto-optical recording medium has the beam diameter of 1/n as in SIL 102. In such a way, SIL 102 is employed to achieve an effect similar to the effect obtained by multiplying the numerical aperture of objective lens 106 by n.
It is noted that a magnetic field coil (magnetic head) 105 and SIL 102 are formed at a slider 104. Information is recorded by irradiating with a light beam magneto-optical recording medium 103 to which magnetic field is applied by magnetic field coil 105.
According to Reference 1, the optical head and the magnetic head are opposite to each other with a disk therebetween. Consequently, the size of the device becomes large and it is impossible to utilize both surfaces of the disk.
According to Reference 2, the optical head and the magnetic coil for recording are placed on the same side of the disk. In this case, both surfaces of the disk are available. However, there arises problems listed below.
1. The size of the device is enlarged since the solid immersion lens and the magnetic recording coil are formed at the slider.
2. Reproduction from the thermomagnetic recording medium is impossible since the medium employed is the magneto-optical medium and no magnetic head for reproduction is provided.
3. A magnetic reproducing head in the thermomagnetic recording and reproducing method should be placed in close proximity to a portion which is irradiated with a light beam. However, in the structure of the magnetic head according to Reference 2, the head cannot be placed in the close vicinity of the portion where the light beam is emitted.
An object of the present invention is to provide a magneto-optical head device capable of recording and reproducing information at a high track density and a high line density and capable of recording and reproducing information on and from both surfaces of a disk.
Another object of the present invention is to provide a magneto-optical head device which can be decreased in size.
Still another object of the present invention is to provide a recording and reproducing device capable of recording and reproducing information at a high track density and a high line density and capable of recording and reproducing information on and from both surfaces of a disk.
A further object of the present invention is to provide a recording and reproducing device which can be decreased in size.
According to one aspect of the present invention, a magneto-optical head device includes a light source, an objective lens which condenses a light beam emitted from the light source, an auxiliary lens which converts the effective numerical aperture of the light beam condensed by the objective lens to irradiate a recording medium with the light beam, and a magnetic reproducing head integrated into the auxiliary lens.
Owing to the magnetic reproducing head which is integrated into the auxiliary lens, the magneto-optical head device can be decreased in size and information recorded on both surfaces of a disk can be reproduced. Further, if a thermomagnetic recording medium is employed as a recording medium, the magneto-optical head device can reproduce information recorded at a high track density and a high line density.
According to another aspect of the present invention, a reproducing device includes a spindle motor which causes a recording medium to rotate, a magneto-optical head device which reads information recorded on the (recording medium, and a demodulation unit which demodulates information read by the magneto-optical head device. The magneto-optical head device includes a light source, an objective lens which condenses a light beam emitted from the light source, an auxiliary lens which converts the effective numerical aperture of the light beam condensed by the objective lens to irradiate the recording medium with the light beam, and a magnetic reproducing head integrated into the auxiliary lens.
Owing to the magnetic reproducing head integrated into the auxiliary lens, the entire reproducing device can be decreased in size and information recorded on both surfaces of a disk can be reproduced. If a thermomagnetic recording medium is employed as a recording medium, the reproducing device can reproduce information recorded at a high track density and a high line density.
According to a further aspect of the invention, a recording and reproducing device includes a spindle motor which causes a recording medium to rotate, a magneto-optical head device which reads information recorded on the recording medium and writes information onto the recording medium, and a modulation and demodulation unit which demodulates information read by the magneto-optical head device and modulates information to be written onto the recording medium. The magneto-optical head device includes a light source, an objective lens which condenses a light beam emitted from the light source, an auxiliary lens which converts the effective numerical aperture of the light beam condensed by the objective lens to irradiate the recording medium with the light beam, a magnetic reproducing head integrated into the auxiliary lens, land a magnetic recording head integrated into the auxiliary lens.
Since the magnetic reproducing head and the magnetic recording head are integrated into the auxiliary lens, the entire recording and reproducing device can be decreased in size and information can be recorded on and reproduced from both surfaces of a disk. In addition, if a thermomagnetic recording medium is used as a recording medium, the recording and reproducing device can record and reproduce information at a high track density and a high line density.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.